VOX AC15 tube advice needed

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Re: VOX AC15 tube advice needed

Postby (soundmasterg) » Tue Sep 25, 2012 8:13 pm

The overdrive or distortion sound that you get from pedals doesn't sound the same and is not as touch responsive as the overdriven sound from tubes. It can't be emulated very well with pedals at all. Personally I like the stock setup on the AC15 and AC30 as long as good tubes are in place.

It sounds like you are looking for a clean sound out of your amp, with lots of headroom, so if so, using a 12AU7 or a 5751 or a 12AY7 would be the way to go. I recommend against using a 12AV7 as it is a high current preamp tube and won't really sound good in any of the positions in your amp. The 12AY7 would be a much better choice as it has similar gain and is not a high current preamp tube so its bias will be much closer to ideal when put into your amp.

If you find you don't get good service from the place you took your amp, there are several places and people in the Portland area who do good amp work including me, though I have been very busy with school and work and haven't had much time to work on amps. Hopefully they do a good job and you are happy with the work!

Greg
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Re: VOX AC15 tube advice needed

Postby (brammy) » Sat Oct 06, 2012 4:47 pm

ok..... based on lots of advice, here is where I'm at for my VOX AC15

AC15 TUBE LAYOUT
V1 is closest to the power switch and the board is marked V1-V5 The 2xEL84s are just below the 5xECC83 and the 1x5Y3 rectifier is located to the right of the ECC83s

V1 - Phase Inverter: 12AT7 (Electro-Harmonix 12AT7 http://tubedepot.com/eh-12at7.html)
V2 - Tremolo: 12AX7
V3 - Reverb: 12AX7
V4 - Pre amp - Tone Driver: 12AX7
V5 - Pre amp - Gain Stages: Jan 5751 http://tubedepot.com/nos-5751jan.html... Mullard 12AU7 wold be even better but its very expensive
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Re: VOX AC15 tube advice needed

Postby (wmthor) » Sun Oct 07, 2012 1:08 am

When needed, I buy all my tubes from KCA NOS Tubes.
'98 360 LH MG
'63 1000 FG (it belongs to my nephew now)
'96 1997 LH MG
'00 360/12 Carl Wilson LH FG
'07 730S Shiloh LH
'97 360/12v64 LH FG
'08 660/12 LH FG
'40s DC-12 Lap Steel (it belongs to my nephew now)
'15 4003 LH FG
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Re: VOX AC15 tube advice needed

Postby (brammy) » Sun Oct 07, 2012 2:11 am

Thanks... I'll compare that to Tube Depot
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Re: VOX AC15 tube advice needed

Postby (Folkie) » Sat Oct 20, 2012 8:29 pm

Kent,

About six months ago I purchased a Vox AC15C1 and had Gary at North Coast Music replace the stock Celestion Greenback with a real Alnico Blue speaker. I hadn't done any research about upgrading the tubes until I came across this thread. When you say that you use your AC15 for clean tones only, does that mean mostly with Rickenbacker guitars? The reason I ask is that I use mine almost exclusively with my two 12-strings, and, although the amp sounds pretty good with both my 330/12 and my 360/12, I'm wondering if I can glean something from your extensive research on this matter. If you use you AC15 primarily for clean "jangly" tones, then I may have my tubes replaced with the exact ones you recommended. Do you have any words of advice on this subject?

Robert
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Re: VOX AC15 tube advice needed

Postby (brammy) » Fri Nov 02, 2012 3:23 pm

Folkie wrote:Kent,

About six months ago I purchased a Vox AC15C1 and had Gary at North Coast Music replace the stock Celestion Greenback with a real Alnico Blue speaker. I hadn't done any research about upgrading the tubes until I came across this thread. When you say that you use your AC15 for clean tones only, does that mean mostly with Rickenbacker guitars? The reason I ask is that I use mine almost exclusively with my two 12-strings, and, although the amp sounds pretty good with both my 330/12 and my 360/12, I'm wondering if I can glean something from your extensive research on this matter. If you use you AC15 primarily for clean "jangly" tones, then I may have my tubes replaced with the exact ones you recommended. Do you have any words of advice on this subject?

Robert


Hi.... my amp has been out of service since I moved over 5 years ago. I'm having it looked at now... the guy says he replaced a cap or two and fixed the reverb and that it sounds great.... I still need to go pick it up, so I haven't had a chance to try the new tube setup.

I cant say that I have any great advice or pearls of wisdom except for this.... as I described, switching out the gain preamp with something like a 12AU7 WILL really change the sound of the amp.... for me I think it will be a great change, although for some people who want very loud and want to get that high volume breakup it would not be the way to go.

As for the sound I was looking for while in the band.... yes, over 90% of the time I was using a RIC 360 6-string (also used an Epiphone Sheraton II and also an Ibanez Artist) but it wasn't only a jangly sound I was after... I'd say it was more clean/mellow/sweet as opposed to rockin/crunch/distorted. The main thing I found is that if you achieve the clean and sweet sound then it is easy to get the other distorted sounds via various pedals..... but if your amp is spitting out a crunchy broken up sound then no pedal in the world will get you back to clean and sweet.

One thing to think about is that my AC15 is a "Korg era" while yours is newer. For your particular amp, you will want to check exactly where the Preamp Gain Tube is.... for my AC15 it is the 5th tube away from the power switch, but your amp might be different. Hope this helps.... please let us all know how it goes.

V1 - Phase Inverter: 12AT7 (Electro-Harmonix 12AT7 http://tubedepot.com/eh-12at7.html)
V2 - Tremolo: 12AX7
V3 - Reverb: 12AX7
V4 - Pre amp - Tone Driver: 12AX7
V5 - Pre amp - Gain Stages: Jan 5751 http://tubedepot.com/nos-5751jan.html... Mullard 12AU7 wold be even better but its very expensive
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Re: VOX AC15 tube advice needed

Postby (Folkie) » Fri Nov 02, 2012 9:26 pm

Thanks Kent,

I am definitely looking for a clean, jangly sound, rather than a mellow "sweet" one, and I've been able to get lots of loud, clean tones from the amp without any breakup. (I just don't use the amp for dirty or overdriven tones.) The Alnico Blue speaker is a real blessing. Still, I feel like I'm falling short of the ideal 12-string tone and would like a little more compression and chime. I've tried my JangleBox JB2 with the amp, and have decided I like the tone better without it. I'll certainly keep in mind your tube suggestions, particularly the 12AU7 in the gain preamp. Does anyone else out there have any insights?

Robert
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Re: VOX AC15 tube advice needed

Postby (sloop_john_b) » Thu Nov 08, 2012 12:41 pm

Folkie wrote:Thanks Kent,

I am definitely looking for a clean, jangly sound, rather than a mellow "sweet" one, and I've been able to get lots of loud, clean tones from the amp without any breakup. (I just don't use the amp for dirty or overdriven tones.) The Alnico Blue speaker is a real blessing. Still, I feel like I'm falling short of the ideal 12-string tone and would like a little more compression and chime. I've tried my JangleBox JB2 with the amp, and have decided I like the tone better without it. I'll certainly keep in mind your tube suggestions, particularly the 12AU7 in the gain preamp. Does anyone else out there have any insights?

Robert


Do your 12-strings have toasters or higains?
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Re: VOX AC15 tube advice needed

Postby (Folkie) » Thu Nov 08, 2012 10:34 pm

John,

Both my 1991 330/12 and my 2010 360/12 now have 7.4k toasters. Both sound good through my Vox AC15, but the consensus here seems to be that replacing the stock tubes can really improve tone by leaps and bounds. I'd be interested to hear any additional thoughts you have on this matter. :)

Thanks,

Robert
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VOX AC15 tube advice needed

Postby (8mileshigher) » Thu Nov 29, 2012 7:23 pm

Folkie wrote: Still, I feel like I'm falling short of the ideal 12-string tone and would like a little more compression and chime. I've tried my JangleBox JB2 with the amp, and have decided I like the tone better without it. I'll certainly keep in mind your tube suggestions, particularly the 12AU7 in the gain preamp. Does anyone else out there have any insights?


Robert, I was surprised to read that if you were looking for more compression and chime, that the Janglebox JB2 did not deliver. And you have the Alnico Blue speaker ....so you'd think that should put you in the chime league. I have an AC-30cc, (not an AC-15 model) and I put a JJ brand 12AU7 tube in the V2 socket on the AC-30cc (V2 is the second stage pre-amp gain on the AC-30cc) as it gives more clean head-room. The AC-30cc is not a direct comparison to what you have, but anyway, wanted to share about the properties of the 12AU7 tube in a Vox.

As info, I saw this thread on the Vintage Amps Forum wherein a guy posted that the AC-15c1 model, because it lacks a "Cut" control (which it needs), is way too bright sounding with single coil guitars .
http://vintageamps.com/plexiboard/viewt ... me#p980302
It's always useful to check that Forum for tips from knowledgeable people.

That earlier comment made about a Mullard NOS 12AU7 being pricey ---- No Kidding ! ! ! :( I checked that Tube Depot.com site and the Mullard NOS is listed at $249 each ! ! ! :roll:
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Re: VOX AC15 tube advice needed

Postby (brammy) » Sat Dec 01, 2012 6:01 pm

Request for speaker advice

As I said, I have a 1993 (Korg era) VOX AC-15 with a 12", 15 W, 8 ohm G12 Blue Alnico speaker.

I'm also in the process of building a sound isolation box and I'd like to put just a speaker (driven by the AC-15) and mic in that box (not the whole amp due to heat buildup).

I could take the speaker out of the AC-15, but I'd rather not. However, a new G12 is rather pricey:
speaker-1.jpg

Does anyone have any recommendations for a less expensive speaker that might be similar to the G12? Would this one be good?....
speaker-2.jpg

Thanks in advance for any expert advice.
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Re: VOX AC15 tube advice needed

Postby (Folkie) » Sat Dec 01, 2012 6:08 pm

Thanks for the response, Rich. I should say that I very much like the sound I'm getting by running my 12'ers directly into the Top Boost input on my AC15C1. But it's still a little short on the jangle quotient. Part of the reason that I stopped using my JB2 with the AC15 is that I was getting some unruly squeal when I kicked the compressor in. I'm not sure what was causing it, but I decided to go directly into the amp.

I appreciate the tube advice, although I'm not so sure I need more clean headroom: my AC15C1 can get VERY loud without breaking up at all. By the way, my amp does hava a Tone Cut knob. And, as you can gather from what I've said, I've noticed no problems with excess, "harsh" treble.

I'll probably leave the stock tubes in the amp for a while, and, if it turns out the tone needs a push, I may take your advice and invest in a new JJ brand 12AU7 tube.

I always value your advice and expertise. I hope your AC30 is jangling!

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VOX AC15 tube advice needed

Postby (8mileshigher) » Mon Dec 03, 2012 11:57 pm

Folkie wrote:Part of the reason that I stopped using my JB2 with the AC15 is that I was getting some unruly squeal when I kicked the compressor in. I'm not sure what was causing it, but I decided to go directly into the amp.
Robert


I have the Original Black JangleBox and I have found with trying it with half a dozen different amplifiers (not just a Vox) that anytime I push the Janglebox Gain and Attack knobs past 2 o'clock posiiton that I am inviting squeal and feedback. I assumed this was a function of the JB "Gain" setting .... I just turn the JB down and can get the Byrdsy sound when I want it on the Bright setting, and I also use the JB on the "Dark" setting on several tunes that gives it a nice tone as well as the Normal setting.

I assume the squeal/feedback is avoided by reaching the optimum equilibrium settings between the Amp's pots, the Guitar's pots and the Janglebox's own settings.
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Re: VOX AC15 tube advice needed

Postby (Folkie) » Tue Dec 04, 2012 7:22 am

Thanks, Rich! That was very helpful. But I wonder why I only get the squeal from my Vox AC15, and not from my solid state Fender Princeton Chorus amp. When I first described the problem to Gary at North Coast Music, he said I probably had a microphonic tube, and he referred me to an authorized Vox service center called Empirical Sound. They tested the amp repeatedly and found nothing wrong. So I paid their bench fee and took the amp home, only to find that the squeal was still there. Frustrating, but I can almost reach "the sound" without my JangleBox. I'll try to tweak all my settings, as you recommended, in order to get rid of the noise. Any other words of advice?

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Re: VOX AC15 tube advice needed

Postby (admin) » Tue Dec 04, 2012 7:35 am

Robert not as empirical a test as you needed? Why did the techs not test the amplifier with the JB2?

All of this aside you may find a Fender Deluxe reverb more to your liking when it comes to the JB2 and the 12 string.

Also have you contacted JangleBox?
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